Shock Swap with 99-02 R6

[Ash797]

Any updates???

 

[Formula390]

Any updates???

I've got all the parts from RaceTech, but haven't rebuilt and put anything on, or done a test ride yet. I have no good excuse other than It's Texas, it's July, it's REALLY friggen hot out, humidity is hovering somewhere around 9 billion percent (sweat literally started POURING off me yesterday standing at the back of my trailer considering options on how to unload a machine tool... that's right, it's literally too hot out to even THINK outside right now...) and frankly, I just haven't been motivated to do anything other than hide in the air conditioned shop and work on other projects. If it's any consolation I have been giving a lot of THOUGHT into doing it... but that seems to fall flat the moment I step out of the air conditioning. I'm trying to get to it, but motivation to spend half a day upside down bashing my knuckles and blinking sweat stinging in my eyes hasn't been incredibly pressing... Just being completely honest there.

 

[SPG]

I have one rebuilt, installed, and should be racing it this weekend if everything works out. I'll have a better idea after that...
-Sean

 

[mr-fabricator]

Winter here , cold and wet track pretty much every weekend , got the parts just need to install , still waiting on front springs also so wanted to do fromt and rear at the same time .

Om a side note a new club is setting up near me for upto 500cc bikes theyre also looking into endurance racing so this shock is gonna work a treat as i dont think the stock one would hold upto 5 hours of punishment and no adjustability between 2 riders . My team mate ( he doesnt know yet ) is 20lb heavier than me to , hopefully it all works out.

 

[SCUBA]

At 200lbs, I don't see a listing for a 12.5 r6 spring. Will I need to call and special order or do you have a part number.

 

[mr-fabricator]

Racetech mate , just call a retailer , u just need dimensions , cant remember off the top of my head but should be on this thread . U need i/d of spring and length then ask for a 12.5 in that size .

not limited to racetech but do go for a quality brand .

 

[Ryanthegreat1]

I have been riding around on the R6 shock with the RC spring on the lightest preload, it is too soft for spirited street riding. I am dragging the belly pan on the fun roads. And I am hammering the bump stops front and rear. To be fair, FS25 is a rough road with a lot of frost heaves and holes.

The dampening on the R6 shock is still far superior.

 

[mr-fabricator]

If your bottoming out wont a bit of preload help ??

 

[Ryanthegreat1]

But then I have no static sag. The spring is just too soft for my weight. It feels well balanced with the front now. Just too soft all around for what I am doing.

 

[reenmachine]

Explain to me why static sag matters. Wouldn't it only matter how much sag you have when you're on it?

 

[mr-fabricator]

If u have zero static sag and when u hard brake , as the weight transfers forwards the rear has nothing left to give and the rear wheel will come off the ground , certainly loose near all traction and grip , .

Basicly if u have 15mm static and lift the bike 10mm u still have tires on the ground and grip , if u have 0 static sag and u lift the bike 10mm ( 1mm for that matter ) u have left this earth and all the grip it provides .

Hope that makes sense .

 

[psych0hans]

Hi guys, has anyone tried to fit the RC8 rear shock on the 390? Or is this not possible? Sorry, if it's been mentioned before, but I don't recall reading about it.

 

[Formula390]

Hi guys, has anyone tried to fit the RC8 rear shock on the 390? Or is this not possible? Sorry, if it's been mentioned before, but I don't recall reading about it.

The RC8 shock is much shorter than even the stock RC390 shock. The RC8 also uses that screwy pivot linkage so it's valving and spring would be TOTALLY wack for swapping onto the 390, so overall, just not a candidate for a shock swap.

An ideal length for the RC390 is something around 305-310mm, with the stock length being 300. This is why racers are opting for a slightly longer shock and why the 99-02 R6 shock was a viable candidate for swapping as a core, because it's length is 304mm. In an ideal world, we've have an extra 6mm length, but for a core to build from, it's as good a starting point as we are likely to find it seems. Some MIGHT be able to get away with just changing the spring on the stock R6 shock, but most likely unless you find a REALLY clean low miles shock, you are looking at the shock being 13-15 years old. A full rebuild is certainly a good choice, with replacing all the seals, bumper, changing the oil, and recharge the nitrogen. Is it REQUIRED... well, maybe. Maybe not. Another spring is CERTAINLY necessary, but you might get lucky and be able to leave the rest of the shock alone and just use it within it's range of adjustability. If it then starts to leak, or bleed down, or the bumper falls apart... well, then throw another stock R6 shock at it. It's a budget option for those being excessively cost conscious. Would I run it like that on MY bike, nope. Not a chance... but I also have the knowledge and ability to rebuild the shocks. That may be out of the reach for some, and certainly the nitrogen recharge requires special equipment. I wouldn't recommend doing the rebuild for someone who has no experience with rebuilding a shock previously as a first project to be certain, especially when it's so cost effective to have a suspension shop rebuild it to your specifications. The knowledge that you effectively then have a new shock, which will give you many years of service, is preferable to me to riding around on a shock that might spill it's guts tomorrow, next month, or maybe years from now. You just don't have any way of knowing. Or buy a completely brand new JRi or Ohlins. That's probably the way to go for racers, track day riders, and the more serious street riders who are able to afford it. $0.02.

 

[Formula390]

Explain to me why static sag matters. Wouldn't it only matter how much sag you have when you're on it?

If u have zero static sag and when u hard brake , as the weight transfers forwards the rear has nothing left to give and the rear wheel will come off the ground , certainly loose near all traction and grip , .

Basicly if u have 15mm static and lift the bike 10mm u still have tires on the ground and grip , if u have 0 static sag and u lift the bike 10mm ( 1mm for that matter ) u have left this earth and all the grip it provides .

Exactly! What I was taught is you want 1/3rd of the travel taken up by static and rider sag. If you have to add say, more than 10mm of preload, you losing static sag. This is why the range of adjustment between full load and least load on the stepped adjuster seems to be so small, and why variable rate springs are usually used on stock bikes to give the most range of adjustment... but, load that preload up to max, and all that static sag goes away. So, heavier riders are always complaining that "I don't have enough spring". The heavier riders then have to load the preload up like crazy to get their rider sag right, but have zero static remaining. As noted, zero static sag, and your suspension is now your tire, not the shock. If you have a heavier spring, you dial in less preload, and still have static sag, and still get your rider sag correct.

Of course, sag is just ONE part of setting up suspension, but it's also the one that is easiest for most to understand and is the starting point for tuning. Adjustments to rebound and compression damping can't really be tuned if your sag is totally off. So, you start with sag. That gets your spring setup correctly. From there, then you can start to tune the rest of the settings on your shock. If your sag is screwed up tho, you really are just fighting a battle you CAN'T win.

So think of it like this, preload sets your static sag, your spring sets your rider sag and does MOST of the suspension work. The adjustments for rebound and compression then control what the spring does. So, if you've got the wrong spring to start with, there is NO WAY to setup the shock correctly.

Does that maybe explain things a bit more / help with understanding shock tuning & setup?

 

[Treachery]

Formula390 for forum suspension guru!!!

 

[psych0hans]

Formula390 for forum suspension guru!!!

I second that motion!!!

 

[reenmachine]

If u have zero static sag and when u hard brake , as the weight transfers forwards the rear has nothing left to give and the rear wheel will come off the ground , certainly loose near all traction and grip , .

Basicly if u have 15mm static and lift the bike 10mm u still have tires on the ground and grip , if u have 0 static sag and u lift the bike 10mm ( 1mm for that matter ) u have left this earth and all the grip it provides .

Hope that makes sense .

The RC8 shock is much shorter than even the stock RC390 shock. The RC8 also uses that screwy pivot linkage so it's valving and spring would be TOTALLY wack for swapping onto the 390, so overall, just not a candidate for a shock swap.

An ideal length for the RC390 is something around 305-310mm, with the stock length being 300. This is why racers are opting for a slightly longer shock and why the 99-02 R6 shock was a viable candidate for swapping as a core, because it's length is 304mm. In an ideal world, we've have an extra 6mm length, but for a core to build from, it's as good a starting point as we are likely to find it seems. Some MIGHT be able to get away with just changing the spring on the stock R6 shock, but most likely unless you find a REALLY clean low miles shock, you are looking at the shock being 13-15 years old. A full rebuild is certainly a good choice, with replacing all the seals, bumper, changing the oil, and recharge the nitrogen. Is it REQUIRED... well, maybe. Maybe not. Another spring is CERTAINLY necessary, but you might get lucky and be able to leave the rest of the shock alone and just use it within it's range of adjustability. If it then starts to leak, or bleed down, or the bumper falls apart... well, then throw another stock R6 shock at it. It's a budget option for those being excessively cost conscious. Would I run it like that on MY bike, nope. Not a chance... but I also have the knowledge and ability to rebuild the shocks. That may be out of the reach for some, and certainly the nitrogen recharge requires special equipment. I wouldn't recommend doing the rebuild for someone who has no experience with rebuilding a shock previously as a first project to be certain, especially when it's so cost effective to have a suspension shop rebuild it to your specifications. The knowledge that you effectively then have a new shock, which will give you many years of service, is preferable to me to riding around on a shock that might spill it's guts tomorrow, next month, or maybe years from now. You just don't have any way of knowing. Or buy a completely brand new JRi or Ohlins. That's probably the way to go for racers, track day riders, and the more serious street riders who are able to afford it. $0.02.

Yes, I completely understand the concept of sag. What I thought you were talking about and calling static sag was sag without the rider's weight on the bike. I thought I had read people talking about wanting x amount of sag with the bike just sitting there on its own, and then x+y sag under the rider's weight. I didn't get the concept of needing sag without the rider's weight involved.

 

[SPG]

The usefulness of static sag vs rider sag, is it provides an extra data point for proper spring weight. Otherwise, you could use nearly any weight spring and get the sag adjusted correctly. If use a valve spring and preload it to coil bind at 30mm with the rider on it... my "rider sag" will be correct, but my static sag will also be 30mm. If the spring is too heavy, I could run no preload and get the 30mm with the rider, but I would have zero static sag. Neither of these examples would provide any sort of decent suspension travel or compliance. Having closer to 10mm static and 35 rider sag shows that the spring is more suited to the weight of the bike and rider combination.

Probably a crappy explanation, but hopefully it helps.
-Sean

 

[SPG]

Also, after racing all weekend, the R6 shock worked well. No complaints. It dominated the Ninja 250 classes and I got a second in the 125GP/Moto3 race.
-Sean

 

[reenmachine]

The usefulness of static sag vs rider sag, is it provides an extra data point for proper spring weight. Otherwise, you could use nearly any weight spring and get the sag adjusted correctly. If use a valve spring and preload it to coil bind at 30mm with the rider on it... my "rider sag" will be correct, but my static sag will also be 30mm. If the spring is too heavy, I could run no preload and get the 30mm with the rider, but I would have zero static sag. Neither of these examples would provide any sort of decent suspension travel or compliance. Having closer to 10mm static and 35 rider sag shows that the spring is more suited to the weight of the bike and rider combination.

Probably a crappy explanation, but hopefully it helps.
-Sean

That makes perfect sense -- it's a tool to help get you in the right family of spring rates vs. in some realm where you technically have the right rider sag but still an overall poor setup. I get it.